Muffle for use in connection with the casting of precious metals



June 25, 1935. K. PLASCHKA 2,006,148

MUFFLE FOR USE IN' CONNECTION WITH i'I'iE CASTING 0F PRECIOUS METALS .Fi-led Jan. 27, 1934 Patented June 25, 1935 UNITED STATES MUFFLE FOR USE IN CONNECTION WITH THE CASTING OF PRECIOUS METALS Karl Plaschka, Vienna, Austria Application January 27,1934, Serial No. 708,556 In Austria January 10, 1933 1 Claim. (01. 22-651) This invention relates to an improved type of muflie for use in connection with the casting of precious metals, for the melting down of the latter and for charging the molds. The casting of precious metals, for dental purposes, goldsmiths work, and the like, has hitherto been effected by means of open cup-shaped muiiles mounted on a horizontal centrifuging arm with the discharge aperture of the muflie adjoining the end of the mold inlet. The opposite end of the centrifuging arm is provided with an adjustable counterbalance weight. After the mold (flask) and the melting muiiie have been placed in position, the precious metal charge is placed in the muiiie and melted by a blow-pipe flame, whereupon the centrifuging arm is set in rapid rotation by means of a special slinging device. In consequence of the sudden starting-up of the rotary movement. of the centrifuging arm, in the case of larger charges'the molten precious metal becomes in part forced up the side wall of the open muflie, and is apt to be flung on the upper edge thereof. In this manner loss of material, imperfeet casting, and serious injuries to operators have been likely to occur.

As distinguished from the known types of equipment working in the manner outlined, the muflie according to the present invention is characterized by the essential features, firstly, that the muflie is totally enclosed with the exception of the charging and deliveryapertures, and secondly, that there is provided on the inside of the muiiie v a baflie wall of conchoidal shape which compels the charge to flow towards the delivery aperture with increasing velocity. A constructional example oi' munie according to the present invention is shown in'the accompanying drawing, in.

which:

Fig. 1 shows the l in plan view.

v Fig. 2 is a longitudinal section of the mume.

' Fig. 3 isa horizontal section of the muflle, taken on the line 1-1 of Fig. 2.

y-out of the casting plant Fig.4showsthemumeasseeni planview from above. I I

Fig. 5 is a transverse section of the mume, taken onthelineII-IIotFl8.2.. I

Reterrlngto Fig. 1, the muille a,whichis made in connection with the casting of precious metals oi ceramic material, is completely enclosed except for the charging and delivery apertures, and is adapted to be tightly fitted against the inlet end of the mold h, with the aid of the straining or tensioning means i and'l. The centrifuging 5 arm I is provided at the opposite end with at 001111- ter balancing weight g, and is adapted to be rotated about the pivot point "r. The casting metal is inserted in the solid state at the charging aperture b (see Fig. 2), and heated to melting point by means of a blow-pipe flame. 0n rotation of the arm, the molten material is caused by-dynamic pressure to travel up the side of the muflie into engagement with the conchoidal bafiie e, whence it is directly flung by centrifugal force in a radial direction through the delivery aperture 0 into the mold h. The mufiie is slidingly inserted into a thrusting-up frame on the tensiom'ng plate I, with the aid of the tapered grooves d.

Fig. 3 of the drawing shows, in horizontal section taken on the line II of Fig. 2, the body a of the muiiie, the charging aperture b, and the conchoidal baflie 6 extending into .the interior of the muflie and having an edge extending right up to the delivery aperture 0. Fig. 4 shows, in plan view, the totally enclosed muflle body a, with the charging aperture b and the fitting grooves d.

Fig. 5 is a vertical transverse section of the body a of the muiile, taken on the line II"-II of Fig. 2, showing the inwardly projecting conchoidal baflie e, and the delivery aperture 0. The lower and the two lateral fitting grooves are indicated by broken lines in Fig. 5.

With the described new type 'of muflle for use 

